Vapor storage canister, such as carbon canisters, are used in vehicles to reduce vapor emissions caused by temperature changes in the vehicle. For instance, temperature shifts in the fuel tank which may be caused by diurnal cycles, heat rejection from underbody components such as exhaust pipe and/or hot return fuel from engine can generate fuel vapors in the fuel delivery system. Fuel vapor is also generated during refueling because of air entrainment with liquid fuel, turbulence and temperature difference between tank fuel and fresh fuel. Furthermore for hybrid vehicles, fuel tank is sealed at high pressure. This pressure is released rapidly during refueling. This pressure change can also cause vapor generation. The fuel vapors may leak or permeate from the fuel tank if not properly sequestered. Therefore, in some vehicles fuel vapors are routed to carbon canisters for temporary storage to reduce emissions. The fuel vapors may be subsequently purged during certain operating conditions to prevent overfilling of the vapor storage canister. During purging operation fresh air is introduced into the canister causing desorption of the fuel vapors from the carbon in the canister. Then the mixture of air and fuel vapor is routed into engine via an intake system where they are combusted.
U.S. Pat. No. 8,246,729 discloses a fuel vapor storing device having a tubular diffuser with plurality of openings providing air into the device during purging. However, the fuel vapor storing device disclosed in U.S. Pat. No. 8,246,729 does not provide a desired amount of flow distribution in the device during purging. Specifically, the tubular diffuser may not generate flow patterns which evenly distribute the airflow through the device when purged. The tubular/annular diffuser described in aforementioned patent also increases pressure drop across canister because of narrow flow passages and flow turning. As a result, the desorption rate of fuel vapor into the intake air may be decreased during period of high inlet airflow. Consequently, there may be trade-offs between purging efficiency (e.g., the amount of fuel vapor purged from the canister per volumetric airflow) and the flow-rate of air during purging. As a result, a desired amount of fuel vapor may not be purged from the device in a desired period of time, preventing the device from being completely purged. Consequently, the device may reach maximum vapor storage, thereby increasing fuel vapor emission from the vehicle. This may be particularly problematic in plug-in electric hybrid vehicles (PHEV) where high purge rates are desired due to the limited window of engine combustion operation in the vehicle.
The inventors herein have recognized the above issues and developed a vapor storage device. The vapor storage device includes a diffuser plate positioned on an axis of an inlet port and comprising one or more openings extending through the plate from a leading edge to a trailing edge and a dome coupled to the inlet port of the device and the diffuser plate, where the dome includes side walls spaced away from the diffuser plate.
The dome and the diffuser plate enable uniform flow distribution even at high air flow rate in the canister while purging fuel vapor when compared to previous canisters which do not include domes or diffuser plates. Moreover, the dome and the diffuser plate do not unduly increase pressure losses in the device. Therefore, air may be introduced into the device during purging at a high flow rate while achieving a desirable fuel desorption rate. Consequently, diurnal and/or resting loss emissions are reduced and fuel economy is enabled in the vehicle in which the vapor storage device is included. Therefore, it will be appreciated that the technical results achieved by the vapor storage device include achieving uniform flow distribution of high velocity intake air introduced into the vapor storage device without unduly increased pressure losses in the device, thereby decreasing the amount of time needed to purge the device.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the above summary is provided to introduce a selection of concepts in simplified form. These concepts are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.